Registers


A register consists of a collection of binary storage cells, each implemented by a flip-flop. The number of cells determines the length of the register and, therefore, the length of the binary word stored within the register. Thus, an bit register contains n flip flops and can store n bits ( 2^n binary combinations, or distinct states.)

Operation associated with a register:

  • Write (Load): To load bits of information into the register. Each information bit is input to one of the registers.
  • Read: Reading the content of the register. We simply access the Q output of the register.
Parallel register

Since the read and write operations are applied to all the cells simultaneously, the register is called parallel register.

Three bit parallel register

Parallel to serial register:

  • g=0: Di receive the Pi value. This is the step of getting the parallel signal. All the flip flop should receive their values .
  • g=1: Di receive the Qi-1 value. This is the serial step.
Shift register:
A shift register consist of flip flops connected such that the output of one flip flop feeds the input of the next flip flop. The clock input of all the flip flops is  connected to a common clock pulse source. The number of flip flops in the chain determines the length of the shift register.

Four bit shift register  (also-  'serial to parallel'.)

Serial Binary adder


Note:

  1. The upper register is receiving the input from s so at the end the shift register will contain the output.
  2. The button D-FF retain the array bit from the next clock.

Implementing sequential system using shift register

    Implementing detection of without overlapping "10010":